Disposable flexible material bags for these purposes made of two layers of flexible plastics material have been known for a considerable time. The layers derive either from separate sheets or from a flattened sleeve of plastics material. In for example U.S. Pat. No. 2,894,510 there is a typical disclosure of a flattened sleeve heat sealed across spaced-apart positions to define a container between the seals and with a plurality of ducts penetrating the seal at one end by being sealed between the layers. Two of the ducts are additive and outlet ports, respectively, each having a frangible membrane across it so as to isolate the inside of the container from the outside and yet allow efficient access to the contents via a hollow needle inserted through them. A third duct is a comparatively lengthy inlet tube. The ports are not always provided all at one end, see for example U.S. Pat. No. 2,702,034, and this latter also illustrates that there may be any required number of ports. Once the container has been filled via the inlet tube, that tube is sealed off and the whole is sterilized.
The present invention is concerned with the problem of preserving the sterility of the outer ends of the ports, i.e. the ends outwardly beyond the membranes. As far as the inside of the container is concerned there is little problem since the flexibility of the material of the container allows for the expansion which will occur on the heat treatment involved in sterilization, but considerable problems have arisen in conserving the sterility of the outer ends of the ports. In U.S. Pat. No. 2,896,619 for example additional tabs or sheets are secured around the outer end of these ports so as to form a cap over that outer end and this cap is torn open by the user to gain access to the port. However this has involved the provision of extra tabs, i.e. extra parts. These involve an extra manufacturing step and extra material and moreover are not entirely reliable since their securing presents difficulties and the volume which they contain is not entirely reproducible. There have been cases where these protective caps have burst under sterilization or have sprung a leak. Plugs have also been used, see for example U.S. Pat. No. 3,209,752, but are even more likely to be blown off by the expansion of entrapped air.
A similar idea has been applied to preserving the sterility of an inlet port defined by a self-sealing pad on a face of a container; see for example U.S. Pat. No. 2,704,075.